The series hybrid electric vehicle designates a vehicle configured to drive an electric generator by an internal combustion engine (engine), to supply electric power from the electric generator to a motor, and to drive drive-wheels by the motor, as disclosed in US2007/0137908 A1, as an example. In a series hybrid electric vehicle, the engine is dedicated to generating electric energy, and the mechanical energy generated by the engine is not directly transmitted to the drive-wheel, in contrast to a parallel hybrid electric vehicle where some mechanical energy generated by an engine is directly transmitted to a drive-wheel.
One example of a hybrid electric vehicle is described by US2007/0137908 A1. This example discloses a hybrid electric vehicle configuration that uses a diode rectifier to reduce the loss of electric energy generated by a system by rectifying current generated by a generator driven by the engine and then driving a motor connected to the vehicle driving system. In this reference, an inverter is provided between the diode rectifier and the motor, and the motor is driven by alternating current from the inverter that converts a direct current rectified by the diode rectifier to alternating current.
However, the inventors have found that providing plural feed circuits for the motor and using either one or both of the feed circuits depending on an operating condition is preferable for boosting efficiency of the hybrid electric vehicle and/or prolonging life of components of the hybrid electric vehicle.
The technology described in the reference above does not utilize plural feed circuits. In this way, the approach used in the reference above may reduce efficiency of a hybrid electric vehicle and may further cause element(s) connected to the feed circuit to deteriorate.
Some embodiments of the present disclosure provide a control system or a control method for a hybrid electric vehicle to improve efficiency and to prolong the operational life of components of the hybrid electric vehicle. For example, an embodiment may provide plural feed circuits for a motor and use either or both of the feed circuits depending on an operating condition.
One embodiment of the present description includes a control system for a hybrid electric vehicle, the hybrid electric vehicle comprising: a generator driven by an engine to generate alternating current; a motor configured to provide a drive force to propel the vehicle and configured as a generator to regenerate energy during vehicle deceleration; a rectifier to rectify alternating current generated by the generator; an inverter connected to a feed circuit between the rectifier and the motor to convert direct current in the feed circuit into alternating current; a power supply connected to a line connecting the rectifier with the inverter; a first feed circuit to supply a current to the motor via the inverter; a second feed circuit to supply a current to the motor while bypassing the inverter, wherein the second feed circuit includes an alternating current converter. The control system may include a current calculating module to calculate a current, the current being at least one of a current to drive the motor and a current generated by the motor; and a feed controller to selectively implement a first mode when the calculated current is below a predetermined current value and to selectively implement a second mode when the calculated current is more than the predetermined current value. Either the first feed circuit or the second feed circuit may be used in the first mode and both the first feed circuit and the second feed circuit may be used in the second mode.
This control system can solve at least some of the issues of the related art described above.
In an example embodiment, both the generator and the motor are polyphase alternating current rotating machines, the rectifier is a diode rectifier, and the alternating current converter is a plurality of semiconductor switches that are provided for each phase for the polyphase generator and the polyphase motor.
In another example embodiment, the alternating current converter is a second inverter.
In another example embodiment, both the first inverter and the second inverter have a similar rated current, and the feed controller is configured to activate either the first or second inverter when the calculated current is below a predetermined current value.
In another embodiment, the feed controller may activate one of the first and second inverter, and may activate the other of the first and second inverter when it is decided that only one of the inverters is activated and a temperature of the activated inverter is above a predetermined temperature.
In another example embodiment, the generator can start the engine and can be driven by the engine when the vehicle is started, the system may further comprise a switching device to select a motor power feed mode if the power supply is connected to the motor via the second inverter and to select a starter power feed mode if the power supply is connected to the generator via the second inverter, and may also comprise a controller to switch to the starter power feed mode to start the engine.
As a non-limiting example, relay switch(es) or insulated gate bipolar transistors etc. can be used as an element of the “switching device”.
In another embodiment, a method is provided for controlling a hybrid electric vehicle having a generator driven by an engine to generate alternating current, a motor configured to provide a drive force to propel the vehicle and configured as a generator to regenerate energy during vehicle deceleration, a rectifier to rectify alternating current generated by the generator, an inverter connected to a feed circuit between the rectifier and the motor to convert direct current in the feed circuit into alternating current, a power supply connected to a line connecting the rectifier with the inverter, a first feed circuit to supply a current to the motor via the inverter, a second feed circuit to supply a current to the motor while bypassing at least the inverter, and an alternating current converter provided in the second feed circuit. The method may include calculating a current, wherein the current is at least one of a current to drive the motor and a current generated by the motor; activating one of the first and second feed circuits when the calculated current is below a predetermined current value; and activating both the first and second circuits when the calculated current is more than the predetermined current value.
This method can solve at least some of the issues of the related reference described above.
In an example embodiment, both of the first inverter and the second inverter are set such that they have the same rated current, and controlling feed current is activating either the first or second inverter when the calculated current is below the predetermined current value.
In another example embodiment, controlling feed current is used to activate one of a first and second inverters, and controlling feed current is used to activate the other of the first and second inverters when it is decided that only one of the inverters is activated and a temperature of the activated inverter is above a predetermined temperature.
In another example embodiment, wherein the generator is further configured to start the engine, and the hybrid electric vehicle comprises a switching device for selectively switching between a motor power feed mode if the power supply is connected to the motor via the second inverter and a starter power feed mode if the power supply is connected to the generator via the second inverter, the method may further comprise switching the switching device such that the starter power feed mode is selected to start the engine.